The invention relates to an electrical drive for a wheel hub of a motor vehicle, especially a utility vehicle, with an electric motor disposed within the wheel and having a stator and a rotor, the rotor being connected to a step-down transmission, and having a brake system.
A drive of this kind is disclosed in German patent document DE 41 10 638 A1. By means of the design described therein, the gear transmission, torque converter and drive shafts components are eliminated and thus weight and costs can be saved.
In this drive, however, the large axial width is disadvantageous. Due to the necessary elaboration of the design of this drive, which is represented simply schematically in the disclosure, the drive becomes even wider. If the drive is used in an omnibus, the large overall axial width of the drive results in a relatively narrow aisle for the passengers of the omnibus.
Another problem of the electrical drive represented in DE 41 10 638 A1 is its relatively low continuous power output which is too low for practical use of the omnibus. Attempts to improve the continuous power output of the electrical drive have only led to an additional increase of the overall width of the drive.
Other electrical drives for a wheel hub of a motor vehicle are disclosed in German patent documents DE-PS 21 09 372 and DE-OS 18 06 022. However, these drives also have the disadvantage of a large overall width together with a relatively low continuous power output.
It is an object of the present invention to provide an electrical drive for a wheel hub of a motor vehicle which has an adequate continuous power output and a relatively small overall width.
This and other objects and advantages are achieved by the electrical drive for a wheel hub of a motor vehicle, especially a utility vehicle, with an electric motor disposed within the wheel and having a stator and a rotor, the rotor being connected to a step-down transmission, and having a brake system according to the invention, in which a stator is disposed within a hollow rotor and the step-down transmission is disposed within the stator.
The arrangement of the reduction gear transmission within the stator results in a very small overall width of the electrical drive, since the latter is almost entirely integrated into the contour of the wheel. As a consequence, the electrical drive has an overall width that is slightly larger than the wheel itself. Thus, when the drive according to the invention is used in omnibuses, a substantial amount of room is left for a passenger aisle than was the case previously.
Since the stator is disposed within the rotor, the diameter of the rotor can be made very large. This results in a very large diameter of the air gap between the rotor and the stator. Ultimately, the electrical drive can have a very high power output. This furthermore results in a very high torque, so that the ratio of the step-down transmission can be relatively low.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.